The present invention is directed to improved barrels for firearms and methods of manufacturing the same. In particular, the present invention provides improvements to: gain twists in the rifling of barrels of firearms; the design of a bore in the barrel such that the opening in the muzzle end is of a different diameter than the opening in the breech end (preferably the opening at the muzzle end is of a lesser diameter than the opening in the breech end of the bore of the barrel); varying the angle of the rifling defined in the bore of the barrel; providing a design for a button for forming the gain twist or varying the gain twist by selectively adjusting the rotational speed of the button as it is moved relative to the barrel without shredding the inner surface of the barrel during the manufacture process (preferably the button is designed with a sinusoidal shape periphery); and providing an apparatus for forming the desired gain twist and selectively varying the gain twist at different sections of the barrel during fabrication of the rifling.
Gain twists are provided in barrels of firearms for accelerating the rotational speed of a bullet as it travels from the breech end of the barrel towards the muzzle end of the barrel. Gain twists in the rifling of known firearms progressively increase the rate of twist of the rifling in a direction from the breech end towards the muzzle end of the bore of the barrel so that a bullet travelling through the bore is continuously rotationally accelerated until it is discharged from the opening in the muzzle end. However, constant acceleration of the rotational velocity of the bullet through the entire length of the barrel may diminish both the stability and accuracy of the discharged bullet as it exits the muzzle opening, and thus adversely affect the accuracy of the bullet after it is discharged from the firearm. Bullet performance may also be affected by the respective sizes of the openings in the breech and muzzle ends of the bore of the barrel, by the rate of twist of the rifling in the bore of the barrel, and by the peak pressure in the bore during discharge of the firearm.
Known methods of manufacturing rifling for barrels having a variable gain twist do not employ buttons pulled through the barrel at a variable rates of rotational speed because known button designs will shred the barrel during change in rotational speed. Accordingly, variable gain twists in rifling are currently formed by a cutter or scraper which is a laborious and expensive process. No satisfactory apparatus for manufacture of a barrel having a variable gain twist using the button method of fabrication is currently available.
It is the primary object of the present invention to provide an improved barrel for firearms for enhancing the performance of bullets discharged therefrom. In particular, the objects of the present invention include fabrication of a barrel for firearms having rifling of a variable gain twist and of a fixed twist at selected sections of the barrel; fabrication of a barrel for firearm having relative variable sized openings in the breech and muzzle ends of the barrel; and fabrication of a barrel for a firearm in which the rifling is selectively formed at variable angles relative to the inner surface of the barrel.
Further objects of the present invention include providing an improved button by which a variable gain twist in the rifling is fabricated by moving a button relative to the barrel while simultaneously rotating the button relative to the barrel, the barrel relative to the button, or both, at a variable rotational speed, and providing an apparatus (preferably controlled by a computer) for fabricating rifling in the barrel at a variable gain twist by selectively adjusting the relative rotational speed of the button or barrel as the button is moved relative to different sections of the barrel. It is further within the scope of the invention to fabricate a variable gain twist by electrolysis and acid etching procedures.
Other objects, improvements and advantages of the present invention will become apparent to those skilled in the art from the following discussion.